The bodies of the men aged between 25 and 35 were found on Wednesday night in the Maamel area on the eastern outskirts of Baghdad, police Lieutenant Osama Adnan said on Thursday.
They had no identity papers, he added.
The discovery occurred amid increasing tension between the country's Sunni Muslim minority and the Shia-dominated government of Prime Minister Ibrahim al-Jaafari.
It was not clear if the dead men were Sunnis or Shia.
The influential Sunni Muslim Association of Muslim Scholars and the Iraqi Islamic Party, the country's largest Sunni political group, said they had no information about the incident.
On Wednesday, the association accused Iraqi security forces of detaining, torturing and killing 11 Sunni Arab men, including a cleric.
Sunni groups have also accused security forces of allowing at least nine Sunnis detained last weekend to suffocate after locking them for hours in a van without ventilation as temperatures soared to 46C.
The Iraqi Interior Ministry said both allegations were being investigated, and if true, those responsible would be punished.
There had been tit-for-tat killings between Sunnis and Shia in the past.
On 10 May, clerics and dozens of followers from both groups were killed.